1. Field of the Invention
The present invention relates to a machine for treating a ballast bed underneath a track, comprising a machine frame extending in a longitudinal direction and supported on the track by undercarriages for movement in an operating direction, a suction unit mounted on the machine frame, the suction unit comprising a vertically and laterally adjustable suction pipe having a suction opening for aspirating ballast from the ballast bed, a conveyor band means arranged on the machine frame to convey the aspirated ballast away from the suction unit, a ballast discharge device mounted on the machine frame rearwardly of the suction pipe in the operating direction, the ballast discharge device comprising a hopper, and a track lifting unit mounted on the machine frame.
2. Description of the Prior Art
A machine of this type has been disclosed in copending U.S. patent application Ser. No. 08/313,211, filed Oct. 20, 1994, assigned to the same assignee as the present application. The machine may be used for aspirating and replacing an entire ballast bed underneath a track. With the aid of clearing means, the ballast underneath the track is removed by a suction pipe to a ballast storage container mounted on the machine frame, and the ballast storage container has a discharge opening to discharge the removed ballast onto a conveyor band arrangement. This conveyor arrangement conveys the ballast forwardly over a front end of the machine frame to load the conveyed ballast in a box car coupled to the machine. At the same time, new ballast is conveyed from the rear end of the machine and is discharged from the hopper of a ballast discharge device immediately rearwardly of the clearing means in the operating direction. At the ballast discharge point, the track is held in a desired vertical position by a track lifting unit. There is no provision for partially or fully reusing the removed ballast.
German patent application No. 4,101,432, published Jul. 23, 1992, discloses a machine for lowering a track. A machine frame runs on the track in an operating direction, and the front end of the machine frame carries a track lifting unit as well as a vertically adjustable arrangement for aspirating ballast from underneath the track until a desired track level has been obtained. The aspirated ballast is conveyed to a hopper at the rear end of the machine frame. A screen for cleaning the aspirated ballast is mounted in the hopper and a conveyor band is provided to convey the detritus away from the hopper. At the rear undercarriage, the track automatically rests on the new, lowered level of the ballast bed and, depending on need, the cleaned ballast from the hopper is distributed in the cribs. In a final operating step, the track may then be tamped.